RESPONSE OF WINTER WHEAT TO THE CLIMATE AT DIFFERENT ALTITUDES Ⅲ. SOME PHOTOSYNTHETIC CHARACTERISTICS OF THE PLANT
Li Cunxin, Zhang He and Lin Dehui (Kunming Institute of Botany, Academia Sinica)
The authors have measured in situ daily changes in photosynthe-tic rate, its responses to quantum flux density, and CO2 compensation points of wheat plants (Triticum sativum L. c. v. "Fengmai 13") grown at both altitude localities of 840m (lowland) and 2150m (highland) during seedling, elongation, heading and early filling stages, respectively. The results showed that the feature of daily variation in photosynthetic rate during early growth (seedling and elongation) stages is contrary to that during later growth (heading and early filling) stages. During early stages, the photosynthetic rate of winter wheat grown at lowland is higher than at highland. During later stages, on the contrary, the photosynthetic rate of winter wheat grown at highland is higher than at lowland. At the same time, the light saturation point of both altitude localities is about the same. During early growth stages, the light com-pensation point of winter wheat grown at highland is lower than at lowland; whereas during later stages, the light compensation point of winter wheat grown at lowland decreases and is lower than at highland, but the light compensation point of winter wheat grown at highland is relatively constant. In addition, the CO2 compensation point of winter wheat grown at highland is lower than at lowland. Consequently, in respect to the climatic condition of both localities, the above-described differences are discussed.